ARQ for point to point links

Abstract

An automatic retransmission system offering good latency and overhead characteristics combined with programmable tradeoffs among overhead, latency, and error performance. ARQ (Automatic Repeat reQuest) blocks present at both ends of a link coordinate to automatically attempt to re-send data if that data was not received properly the first time it was sent. Re-transmission from the transmitter (transmitter) is requested by the receiver (Receiver) via a highly reliable “Repeat Request” (RR) mechanism. This RR scheme carries sufficient information back to the transmitter for it to determine which previous transmissions need to be re-sent.

Description

STATEMENT OF RELATED APPLICATIONS[0001]The present application is a divisional of U.S. patent application Ser. No. 10 / 889,309, filed Jul. 12, 2004, which is a continuation of U.S. patent application Ser. No. 09 / 287,212 (U.S. Pat. No. 6,779,146), filed Apr. 5, 1999, which is related to U.S. patent application Ser. No. 09 / 287,214, entitled EFFICIENT MULTIPLE PRIORITY LIST MEMORY SYSTEM, filed Apr. 5, 1999, the contents of all of which are herein incorporated by reference for all purposes.BACKGROUND OF THE INVENTION[0002]The present invention relates to digital communications across error-inducing links and more particularly to systems and methods for ameliorating errors by retransmitting unsuccessfully communicated data upon request.[0003]Retransmitting data upon request is a well-known method for improving error performance in data communication systems where errors are detectable and a link from the receiver to the transmitter is available. Systems that provide this retransmission c...

AI Technical Summary

Benefits of technology

[0008]An automatic retransmission system offering good latency and overhead characteristics combined with programmable tradeoffs among overhead, latency, and error performance is provided by virtue of the present invention. ARQ (Automatic Repeat reQuest) blocks present at both ends of a link coordinate to automatically attempt to re-send data if that data was not received properly the first time it was sent. Re-transmission from the transmitter (transmitter) is requested by the receiver (Receiver) via a highly reliable “Repeat Request” (RR) mechanism. This RR scheme carries sufficient information back to the transmitter for it to determine which previous transmissions need to be re-sent.

Problems solved by technology

A disadvantage of ARQ is that link capacity is in part consumed by requests for retransmission and by retransmitted data.

Thus there is associated overhead.

For example, increased numbers of repeat requests and / or retransmission will improve link error performance but at the expense of link capacity.

Also, ARQ is typically associated with an increase in latency across the link.

On the other hand, some types of traffic, e.g., voice cannot tolerate high latency.

However, voice and other types of traffic increasingly carried by IP networks cannot tolerate high latency but can tolerate somewhat higher error rates.

Current ARQ schemes have difficulty adequately servicing mixes of voice and data traffic because of their differing requirements for latency and error rates.

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